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What the Robot Smells: Models of Gases and Crystals

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What the Robot Smells: Models of Gases and Crystals

Use particle models to compare the gases a robot senses with the solids it is built from.

The modeling app

Read the passage and Table 1. Then answer the questions.

A Robot With a Nose

1The robotics team at Juniper Flats Middle School built a delivery robot that rolls through the halls, carrying supplies from the front office to classrooms. This year, the head custodian asked the team to add an air sensor so the robot could also check the air near the boiler room on its rounds. Team captain Freya Lindqvist and programmer Chidi Anozie worked with their coach, Ms. Paloma Echeverría, to learn what the sensor would be "smelling."

2Everything around the robot is made of atoms. Some substances are made of molecules: small, separate groups of atoms joined together. In a gas, the molecules are far apart and move freely. The same kinds of atoms can be joined in different numbers or patterns, and each arrangement makes a different substance with its own properties. Other substances are extended structures. Their atoms are joined to neighbors in every direction, in a pattern that repeats out to the edges of the sample, with no separate groups. For an extended structure, a formula gives the ratio of the atoms, not a count of the atoms in one group.

3The team's sensor is built to detect carbon monoxide (CO), a gas with no color or smell that can make people sick. It can form when fuel burns without enough air, for example in a boiler that is not working well. The sensor is not set off by carbon dioxide (CO₂), the gas people breathe out.

4The robot's body is made of other substances. Its frame is aluminum, a metal. A thin window of sapphire covers its camera. Sapphire is a crystal made of aluminum and oxygen atoms, and it is so hard that grit from the hallway floor rarely scratches it. The team cleans the window with wipes that hold isopropyl alcohol, a liquid that evaporates quickly.

5Ms. Echeverría opened a modeling app that draws a box of particles from a sample. Each atom is a colored ball, and atoms that are joined touch each other. Table 1 lists what the app showed for six samples.

Table 1. What the Modeling App Showed
BoxSampleParticles in the boxAtoms joined together
AHallway air8 of one kind, 2 of another8 have 2 N each; 2 have 2 O each
BCarbon monoxide10, all alike1 C joined to 1 O
CCarbon dioxide10, all alike1 C joined to 2 O
DIsopropyl alcohol vapor10, all alike3 C, 8 H and 1 O
ESapphire window chipNo separate groupsAl and O, 2 Al for every 3 O
FAluminum frame shavingNo separate groupsAl only, in stacked layers
In Boxes E and F, every atom is joined to neighbors in every direction, and the pattern repeats out to the edges of the sample. Hallway air also holds small amounts of other gases, too few to show up in a box of only 10 particles.
1.
Use Table 1 and paragraph 2. Sort each box by what its model shows.
2.
Use Box D.

The 10 particles in Box D hold atoms in all, and of them are hydrogen atoms.

3.
The sensor beeps for carbon monoxide but not for carbon dioxide. Use Boxes B and C. Why are they different substances, even though both contain only carbon and oxygen atoms?
Question 3 options
4.
Freya wipes the camera window, and the isopropyl alcohol evaporates. Which model of the evaporating alcohol fits Box D and paragraph 2?
Question 4 options

Frame, window and test gas

Use Table 1 and the passage to answer the questions.

5.
Use Box E. A tiny chip of the sapphire window has 10,000 atoms in all.

The chip has aluminum atoms and oxygen atoms.

6.
The frame (Box F) and the window (Box E) both contain aluminum atoms. Which difference in the models best explains why they are different substances?
Question 6 options
7.
Chidi's first drawing of the frame shows aluminum atoms in separate pairs, like the N₂ particles in Box A. Which change would make his drawing match Box F?
Question 7 options
8.
To show how the sensor will be tested, Ms. Echeverría makes a model box that holds 6 CO molecules and 4 CO₂ molecules.

The box holds carbon atoms and oxygen atoms.

9.
Freya says, "Hallway air is one substance made of air molecules, just like Box B is made of carbon monoxide molecules." Do you agree? Write a claim, use evidence from Table 1 and the passage, and explain your reasoning with the particle models.